1. Field of Invention
This invention relates to a system and method of protecting an ink jet print head when the print head is used to print on documents which may have dust particles thereon.
2. Background Information
When an ink jet printer is used to print on documents which carry dust, the printing which results is not as clear as it could be, and, because of the dust, the nozzles of the print head become clogged and require frequent cleaning.
In ink jet printing, as the document to be printed upon passes the print head, tiny droplets of ink "fly" through the air and land on the document. By controlling the sequence of nozzles which are activated, it is possible to form dot matrix characters on the passing document.
The diameters of the nozzles on the print head are smaller than the diameter of a human hair, and as such, they are susceptible to blockage by dust, such as paper dust particles from the passing documents. When a paper dust particle blocks a nozzle, the ink droplets from that nozzle are either deflected or blocked entirely. This results in poor print quality, with the affected characters having deflected or missing dots.
The offending dust particles can generally be removed by wiping the surface of the ink jet head with a "clean room quality" dust free cloth. Occasionally, however, it is necessary to pressurize the ink supply and force some ink through the nozzles in order to "purge" the dust particles from the nozzle. This operation is commonly referred to as a "reprime" operation. Both of these wiping and priming operations are nuisances, and they require the operator of the machine to stop it and to perform a number of maintenance operations.